Osteoarthritis (OA) is a degenerative joint disease, affecting more than 27 million people in the United States alone. Despite the fact that OA is a widespread and debilitating disease, current treatment options are extremely limited and no established disease-modifying therapies exist. The development of therapies that can prevent the onset OA and halt its progression is contingent upon the discovery of non-invasive biomarkers for early disease detection. While MRI can be used to non-invasively visualize morphologic joint degeneration in OA, recent MRI developments show promise for the detection of early biochemical changes in cartilage, prior to the morphologic degeneration. An advanced MRI technique, called T2 relaxation time mapping, is sensitive to early biochemical changes in cartilage and has the potential for early diagnosis of OA. The proposed study aims to evaluate cartilage T2 relaxation time in subjects who have no pain, but are at risk for the development of OA. Preliminary studies have shown promising results linking the spatial distribution of cartilage T2 to the progression of pain in subjects with OA. The results of the proposed study will be valuable in that they will help determine whether early biochemical changes in cartilage, as quantified by T2 mapping parameters, can predict the onset of symptomatic knee OA. In order to address this topic, the following three specific aims are proposed: Aim 1: Cross-sectional Analysis. To determine the relationship between cartilage biochemical composition as quantified using the mean, spatial distribution, and laminar organization of T2 relaxation time, and morphologic knee joint degeneration in the cartilage, meniscus and bone marrow, in patients from the OAI incidence cohort. Aim 2: Prospective Analysis. To determine whether baseline cartilage biochemical composition can predict the presence of symptomatic knee OA, defined as development of pain and an increase in morphologic degeneration in the cartilage, meniscus, and bone marrow after two years. Aim 3: Longitudinal Analysis. To determine whether changes in cartilage biochemical composition are related to the presence of symptomatic knee OA.